In recent years, the Institute of Electrical and Electronic Engineers (IEEE) is promoting standardization for the wireless communication method called Worldwide Interoperability for Microwave Access (WiMAX). The WiMAX includes two standards: the IEEE 802.16d targeted for non-mobile subscriber stations and the IEEE 802.16e targeted for mobile subscriber stations (referred to as “mobile station” below). The IEEE 802.16m as the next-generation standard of the IEEE 802.16e is also being subjected to standardization.
A mobile station according to the IEEE 802.16e or the like makes wireless communication with a macro base station arranged on a wired network called Access Service Network (ASN). In other words, the macro base station makes wireless communication with mobile stations located within a coverage within which a radio wave transmitted from the base station can reach (referred to as “macro cell” below). Generally, the macro base station is large-scaled and installed outdoors, and the macro cell is relatively large, too. Thus, if the macro base station is installed, the wireless communication is enabled within a relatively large coverage, but satisfactory communication quality cannot be obtained in a place where a radio wave cannot easily reach such as inside a building.
Thus, it is considered that a smaller-sized femto base station than the macro base station is introduced in the WiMAX. The femto base station is installed indoors such as inside a home, and a coverage within which a transmitted radio wave can reach (referred to as “femto cell” below) is relatively small.
In the communication system in which the two kinds of base stations such as the macro base station and the femto base station are installed, a handover across different kinds of base stations may occur. That is, when a mobile station being communicating within the macro cell moves into the femto cell, the communication party of the mobile station is switched from the macro base station to the femto base station.
At the time of the handover across the macro base station and the femto base station, a service flow established between the mobile station and the base station as handover source is taken over to the base station as handover destination, similarly to a handover between the base stations of the same type. Thus, the mobile station can continue the wireless communication by using the same service flow both after the handover and before the handover. The service flow is used for, for example, distinguishing data flows such as packets and is established per each Quality of Service (QoS) such as a bandwidth required for the data to be transmitted. Therefore, several service flows having different QoS may be established between a pair of mobile station and base station. Then, each service flow is assigned with a Service Flow Identifier (SFID) unique within one mobile station, and the SFID is assigned by an anchor Service Flow Authorization (anchor SFA) function of a gateway provided in the ASN.
Examples of the conventional techniques are disclosed in Japanese Laid-open Patent Publication No. 2006-166081 and International Publication Pamphlet No. WO 2005-112490.
An Internet Service Provider (ISP) network to which a subscriber's home at which a femto base station is installed subscribes is assumed to be utilized as a line for connecting the femto base station and the ASN. That is, a gateway in the ASN is wired-connected with the macro base station and is also connected with the femto base station via the ISP network. In this manner, the existing ISP network is utilized so that a new connection line does not need to be prepared for introducing the femto base station, thereby rapidly installing the femto base station at a low cost.
On the other hand, if a subscriber's home has already subscribed to the ISP network, a home network may have been formed inside the subscriber's home. That is, a plurality of devices such as server or personal computer inside the subscriber's home may have been connected to a router for connecting to the ISP network. In this case, the femto base station to be newly installed inside the subscriber's home will share one router with the home network. Thus, the femto base station is connected to the gateway in the ASN via the router and the ISP network and is also connected to the home network via the router.
Since the femto base station is connected to the home network, a service flow by which the mobile station within the femto cell accesses the home network may be established. In other words, the femto base station and the mobile station may add a new home network service flow, and the mobile station may exchange data with a device within the home network. At this time, the femto base station assigns an unused SFID to the newly-established home network service flow. Specifically, the femto base station confirms the SFID already assigned to the mobile station by the gateway in the ASN, and assigns an SFID other than the assigned SFID to the home network service flow.
However, when the femto base station assigns an SFID to the service flow, since the anchor SFA function of the gateway in the ASN does not involve the assignment of the SFID by the femto base station, a competition of SFIDs may occur. In other words, when the gateway in the ASN assigns an SFID to a newer service flow after the femto base station assigns an SFID to the home network service flow, the same SFID as assigned to the home network service flow may be assigned to the newer service flow.
In addition, since the gateway in the ASN cannot grasp even an address of each device used within the home network, the gateway cannot recognize the service flow established for the home network and cannot accurately set a rule for classifying the packets to each service flow depending on the QoS.